Search

Abstract.: Prospects for future measurements of deeply virtual Compton scattering are studied in leading order using different simple models for the parameterizations of generalized parton distributions (GPDs). Measurements of the lepton charge and lepton beam helicity asymmetry will yield important input for theoretical models towards the future extraction of GPDs. The kinematics of the HERMES experiment, complemented with a recoil detector, was adopted to arrive at realistic projected statistical uncertainties.

Abstract.: A method is discussed to determine the hitherto unknown u-quark transversity distribution from a planned HERMES measurement of a single target-spin asymmetry in semi-inclusive pion electroproduction off a transversely polarized target. Assuming u-quark dominance, the measurement yields the shapes of the transversity distribution and of the ratio , of polarized and unpolarized u-quark fragmentation functions. The unknown relative normalization can be obtained by identifying the transversity distribution with the well-known helicity distribution at large x and small . The systematic uncertainty of the method is dominated by the assumption of u-quark dominance.

The physics scope of polarized nucleon-nucleon collisions originating from an internal polarized target in the HERA proton beam is summarized. Based on 240 pb−1integrated luminosity at 40 GeV c.m. energy, statistical sensitivities are given over a wide (xF, pT)-range for a variety of inclusive and exclusive final states. By measuring single spin asymmetries unique information can be obtained on higher twist contributions and their pT-dependence. From double spin asymmetries in both photon and Jψproduction it appears possible to measure the polarized gluon distribution in the range 0.1 ≤ xgluon≤ 0.4 with a good statistical accuracy. Drell-Yan pair production asymmetries in doubly longitudinal mode, measurable in the mass range 3 ÷ 10 GeV, allow discrimination between different parametrizations of the polarized light sea quark distributions. In doubly transverse mode access to the quark transversity distribution might become possible. Statistically significant results can be expected in the elastic channel.

Übersicht Durch Protonenbestrahlung können Rekombinationszentren in Siliziumbauelementen in definierter Tiefe erzeugt werden. Dadurch ergibt sich ein neuer Freiheitsgrad für die Optimierung bipolarer Bauelemente. — Durch den Einsatz von Protonenbestrahlung können bei GTO-Thyristoren geringere Schaltverluste und bei Dioden günstigeres Kommutierungsverhalten erzielt werden. Falls die mit der Wasserstoffimplantation verbundene Bildung energetisch flacher Donatoren nicht zulässig ist, könnte stattdessen He-Bestrahlung eingesetzt werden.

The energy-loss spectrum of high energy muons after traversal of a 10 meter iron degrader has been measured with an accuracy of better than 1%. Data taken at energies between 50 and 120 GeV are in agreement with predictions from a Monte Carlo program based on the most recent theoretical descriptions of all relevant processes. The stopping power calculated by this program deviates up to several percent from earlier calculations.